Field of the Invention
The present invention relates to a lift-off method of transferring an optical device layer stacked over a surface of an epitaxy substrate with the intermediary of a buffer layer to a transfer substrate.
Description of the Related Art
In an optical device manufacturing process, an optical device layer formed of an n-type semiconductor layer and a p-type semiconductor layer composed of GaN (gallium nitride) or the like is formed over a surface of an epitaxy substrate such as a sapphire substrate or a silicon carbide substrate having a substantially circular disc shape with the intermediary of a buffer layer. Furthermore, optical devices such as light emitting diodes or laser diodes are formed in plural regions marked out by plural streets formed in a lattice manner to form an optical device wafer. Then, the individual optical devices are manufactured by dividing the optical device wafer along the streets (refer to Japanese Patent Laid-Open No. Hei 10-305420 for example).
Furthermore, as a technique to improve the luminance of optical devices, a manufacturing method called lift-off is disclosed in Japanese Patent Laid-Open No. 2004-72052. In this method, an optical device layer formed of an n-type semiconductor layer and a p-type semiconductor layer formed over a front surface of an epitaxy substrate such as a sapphire substrate or a silicon carbide substrate forming an optical device wafer with the intermediary of a buffer layer is joined to a transfer substrate of molybdenum (Mo), copper (Cu), or silicon (Si) with the intermediary of a joining material such as AuSn (gold tin). Then, the buffer layer is broken by irradiating the buffer layer with a laser beam having such a wavelength as to be transmitted through the epitaxy substrate and be absorbed by the buffer layer from the back surface side of the epitaxy substrate. Then, the epitaxy substrate is separated from the optical device layer and thereby the optical device layer is transferred to the transfer substrate.